1 files changed, 69 insertions, 0 deletions
diff --git a/docs/configuration/nat/nptv6.rst b/docs/configuration/nat/nptv6.rst
new file mode 100644
index 00000000..c09c8336
--- /dev/null
+++ b/docs/configuration/nat/nptv6.rst
@@ -0,0 +1,69 @@
+.. include:: /_include/need_improvement.txt
+
+.. _nptv6:
+
+#####
+NPTv6
+#####
+
+:abbr:`NPTv6 (Network Prefix Translation)` is a form of NAT for IPv6. It's
+described in :rfc:`6296`.
+
+**Usage**
+
+NPTv6 is very useful for IPv6 multihoming. It is also commonly used when the
+external IPv6 prefix is dynamic, as it prevents the need for renumbering of
+internal hosts when the extern prefix changes.
+
+Let's assume the following network configuration:
+
+* eth0 : LAN
+* eth1 : WAN1, with 2001:db8:e1::/48 routed towards it
+* eth2 : WAN2, with 2001:db8:e2::/48 routed towards it
+
+Regarding LAN hosts addressing, why would you choose 2001:db8:e1::/48 over
+2001:db8:e2::/48? What happens when you get a new provider with a different
+routed IPv6 subnet?
+
+The solution here is to assign to your hosts ULAs_ and to prefix-translate
+their address to the right subnet when going through your router.
+
+* LAN Subnet : fc00:dead:beef::/48
+* WAN 1 Subnet : 2001:db8:e1::/48
+* WAN 2 Subnet : 2001:db8:e2::/48
+
+* eth0 addr : fc00:dead:beef::1/48
+* eth1 addr : 2001:db8:e1::1/48
+* eth2 addr : 2001:db8:e2::1/48
+
+VyOS Support
+^^^^^^^^^^^^
+
+NPTv6 support has been added in VyOS 1.2 (Crux) and is available through
+`nat nptv6` configuration nodes.
+
+.. code-block:: none
+
+  set rule 10 source prefix 'fc00:dead:beef::/48'
+  set rule 10 outbound-interface 'eth1'
+  set rule 10 translation prefix '2001:db8:e1::/48'
+  set rule 20 source prefix 'fc00:dead:beef::/48'
+  set rule 20 outbound-interface 'eth2'
+  set rule 20 translation prefix '2001:db8:e2::/48'
+
+Resulting in the following ip6tables rules:
+
+.. code-block:: none
+
+  Chain VYOS_DNPT_HOOK (1 references)
+   pkts bytes target   prot opt in   out   source              destination
+      0     0 NETMAP   all    eth1   any   anywhere            2001:db8:e1::/48  to:fc00:dead:beef::/48
+      0     0 NETMAP   all    eth2   any   anywhere            2001:db8:e2::/48  to:fc00:dead:beef::/48
+      0     0 RETURN   all    any    any   anywhere            anywhere
+  Chain VYOS_SNPT_HOOK (1 references)
+   pkts bytes target   prot opt in   out   source              destination
+      0     0 NETMAP   all    any    eth1  fc00:dead:beef::/48 anywhere          to:2001:db8:e1::/48
+      0     0 NETMAP   all    any    eth2  fc00:dead:beef::/48 anywhere          to:2001:db8:e2::/48
+      0     0 RETURN   all    any    any   anywhere            anywhere
+
+.. _ULAs: https://en.wikipedia.org/wiki/Unique_local_address